Lamp with heat-responsive decoration

ABSTRACT

A lighting product including a holder for an illumination source, a frame, attached to the holder including a back plate having a front surface adjacent to the illumination source, and a layer of a thermochromic material, which is disposed on the front surface of the back plate so as to alter an appearance of the back plate in response to heat emitted by the illumination source.

FIELD OF THE INVENTION

The present invention relates generally to decorative lighting, andspecifically to lamp and candle holders.

BACKGROUND OF THE INVENTION

The use of thermochromic materials in decorative lighting is known inthe art. For example, U.S. Pat. No. 6,544,448, whose disclosure isincorporated herein by reference, describes a luminary device with athermochromic label. A decorative web of heat-shrinkable polymer isheat-shrunk to conform to the shape of a candle or candle holder. Theweb is decorated with a thermochromic ink or pigmentation, which changesvisibly when the candle is burned.

SUMMARY OF THE INVENTION

In embodiments of the present invention, a lighting product comprises aholder for an illumination source, such as a candle, and a frame, whichis attached to the holder. The frame comprises a back plate having afront surface adjacent to the illumination source. A layer of athermochromic material, disposed on the front surface of the back plate,alters the appearance of the back plate in response to heat emitted bythe illumination source.

In a disclosed embodiment, the thermochromic material is opaque atambient temperature and becomes transparent in response to the heatemitted by the illumination source. An image on the front surface of theback plate, beneath the layer of the thermochromic material, becomesvisible as the thermochromic material becomes transparent. The layer ofthe thermochromic material may optionally comprise a second image, whichis visible at the ambient temperature and becomes transparent inresponse to the heat so as to reveal the first image.

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, pictorial illustration of a lighting product, inaccordance with an embodiment of the present invention;

FIGS. 2A and 2B are schematic, pictorial illustrations showing areaction of the lighting product of FIG. 1 to heat emitted by a candle,in accordance with an embodiment of the present invention; and

FIG. 3 is a schematic, sectional illustration of the lighting product ofFIG. 1, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 is a schematic, pictorial illustration of a lighting product 20,in accordance with an embodiment of the present invention. Product 20comprises a frame 21, comprising a base 22 and a back plate 26 mountedon the base. A holder 24 for an illumination source is also mounted onbase 22. In this embodiment, holder 24 is designed to hold a candle, butthe holder may alternatively be adapted to hold any suitable sort ofillumination source, such as an electric lamp or oil with a wick, whichserves as an oil lamp.

Back plate 26 is roughly perpendicular to base 22. The front surface ofback plate 26 (i.e., the surface that is seen by a user or viewer ofproduct 20 and is shown in this figure), adjacent to holder 24, iscovered by a layer of thermochromic material, which responds to heatemitted by the illumination source, as is described further withreference to the figures that follow. Back plate 26 may also comprise acanopy 28, which extends forward over the illumination source in holder24 and may help in capturing the heat emitted by the illuminationsource. A protective plate 30 may be mounted behind the back surface ofthe back plate in order to protect people and objects from exposure tothe hot back plate. Although the elements of frame 21 are shown in FIG.1 as having a certain geometry and decorative features, these aspects ofproduct 20 are shown only by way of illustration. Alternative geometriesand features that fulfill the functions described herein are likewiseconsidered to be within the scope of the present invention.

Reference is now made to FIGS. 2A and 2B, which are schematic, pictorialillustrations showing the reaction of product 20 to heat emitted by acandle 32 in holder 24. FIG. 2A shows the appearance of back plate 26immediately after lighting the candle, whereas FIG. 2B shows the changein appearance of the back plate after heating by the candle for a periodof time.

An image 34 is disposed on the front surface of back plate 26, and alayer of thermochromic material is formed over the image. Thethermochromic material is chosen so that at ambient temperature (forexample, in the range of 20° C.), the thermochromic layer is opaque, andimage 34 is hidden from view, as shown in FIG. 1. As the temperature ofback plate 26 rises, the thermochromic material gradually becomestransparent, and image 34 is revealed, as shown in FIGS. 2A and 2B. Thethermochromic layer may be uniform, so that back plate 26 is blank untilheated by candle 32. Alternatively, the thermochromic material maycomprise a second image (not shown), overlying image 34, so that thesecond image is visible at ambient temperature and becomes transparentin response to the heat from candle 32 so as to reveal the first image.

FIG. 3 is a schematic, sectional view of product 20, taken along theline in FIG. 1, in accordance with an embodiment of the presentinvention. Typically, base 22, back plate 26 and protective plate 30 aremade from a suitable metal, such as brass. Alternatively, some or all ofthese parts may be made from other materials, such as ceramic, glass, orheat-resistant plastic. Although a back surface 40 of back plate 26 isshown in this figure as being in contact with protective plate 30, theremay alternatively be an air gap or other insulating layer betweensurface 40 and plate 30.

A layer 44 of pigment, defining image 34, is disposed on a front surface42 of back plate 26 and is overlaid by a layer 46 of thermochromicmaterial. Layers 44 and 46 may be printed directly onto surface 42, orthey may alternatively be printed on a substrate, such as chromo paper,which is then glued onto or otherwise affixed to the surface. Layer 44may comprise any suitable ink, and image 34 is typically printed in thislayer using a standard monochrome or four-color printing process.

Layer 46 may comprise any suitable type of thermochromic material, suchas a leuco-based ink or pigment, as is known in the art. The type ofmaterial and thickness of layer 46 are chosen so that the layer becomestransparent at the desired temperature. In the kind of design shown inFIGS. 1-3, using candle 32 as the source of heat, layer 46 is typicallyprinted to a thickness of 1.5-2 μm. A dark-colored leuco dye may beadvantageous to hide image 34 completely until back plate 26 is heated.A second image, which is seen when back plate 26 is at ambienttemperature, may be printed in layer 46 or over layer 46 using anadditional thin layer of thermochromic ink.

Alternatively, layer 44 may be omitted, and the desired image may beformed in layer 46 using a suitable thermochromic material so that theimage is invisible at ambient temperature and becomes visible when thethermochromic material is heated.

It will be appreciated that the embodiments described above are cited byway of example, and that the present invention is not limited to whathas been particularly shown and described hereinabove. Rather, the scopeof the present invention includes both combinations and subcombinationsof the various features described hereinabove, as well as variations andmodifications thereof which would occur to persons skilled in the artupon reading the foregoing description and which are not disclosed inthe prior art.

1. A lighting product, comprising: a holder for an illumination source;a frame, attached to the holder and comprising a back plate having afront surface adjacent to the illumination source; and a layer of athermochromic material, which is disposed on the front surface of theback plate so as to alter an appearance of the back plate in response toheat emitted by the illumination source.
 2. The product according toclaim 1, wherein the illumination source is a candle.
 3. The productaccording to claim 1, wherein the frame comprises a base, upon which theholder and the back plate are mounted.
 4. The product according to claim3, wherein the back plate has a back surface opposite the front surface,and wherein the frame comprises a protective plate mounted on the baseadjacent to the back surface of the back plate.
 5. The product accordingto claim 1, wherein the back plate comprises a canopy that extendsforward over the illumination source.
 6. The product according to claim1, wherein the thermochromic material is opaque at an ambienttemperature of the product and becomes transparent in response to theheat emitted by the illumination source.
 7. The product according toclaim 6, wherein an image is disposed on the front surface of the backplate, beneath the layer of the thermochromic material, so that theimage becomes visible as the thermochromic material becomes transparent.8. The product according to claim 7, wherein the image on the frontsurface of the back plate is a first image, and wherein the layer of thethermochromic material comprises a second image, which is visible at theambient temperature and becomes transparent in response to the heat soas to reveal the first image.
 9. A method for lighting, comprising:mounting a holder for an illumination source on a frame comprising aback plate so that a front surface of the back plate is adjacent to theillumination source; and providing, on the front surface of the backplate, a layer of a thermochromic material that alters an appearance ofthe back plate in response to heat emitted by the illumination source.10. The method according to claim 9, wherein the illumination source isa candle.
 11. The method according to claim 9, wherein the framecomprises a base, upon which the holder and the back plate are mounted.12. The method according to claim 11, wherein the back plate has a backsurface opposite the front surface, and wherein the frame comprises aprotective plate mounted on the base adjacent to the back surface of theback plate.
 13. The method according to claim 9, wherein the back platecomprises a canopy that extends forward over the illumination source.14. The method according to claim 9, wherein the thermochromic materialis opaque at an ambient temperature and becomes transparent in responseto the heat emitted by the illumination source.
 15. The method accordingto claim 14, and comprising forming an image on the front surface of theback plate, beneath the layer of the thermochromic material, so that theimage becomes visible as the thermochromic material becomes transparent.16. The method according to claim 15, wherein the image on the frontsurface of the back plate is a first image, and wherein the methodcomprises forming, in the layer of the thermochromic material, a secondimage, which is visible at the ambient temperature and becomestransparent in response to the heat so as to reveal the first image.